This study attempted to identify early behavioral, physical and familial characteristics of young children with a significant discrepancy between intellectual ability and school achievement. Low achievers, followed from the prenatal period to age 7, were compared with their IQ-matched academically successful controls on indices of cognitive and physical development and family characteristics. Wide-spread cognitive deficits and behavioral deviations were found in the preschool period. Indices of socioeconomic status and family structure were more strongly related to low achievement than were indices of physical development and medical status.